[Indications and new developments in pacemaker therapy]. / Indikationen und neue Entwicklungen in der Schrittmachertherapie.

In the course of the past 25 years the indication for pacemaker implantation has changed from AV-block to the sick sinus syndrome in about 40% of patients. In the same period pacemaker technology has developed considerably and today there are, in addition to the ventricular inhibited pacemaker, two-chamber systems (essentially DDD pacemakers) and pacemakers with an increasing pulse rate during physical effort. The new nomenclature, mode of action and hemodynamic implications of the various systems are explained, and recommendations for implantation are given.

[First clinical experiences with the new intracardial electrode "Helifix"]. / Erste klinische Erfahrungen mit der neuen intrakardialen Elektrode "Helifix".

A new pervenous non-traumatic screw-in electrode has been developed and tested in 61 patients. Dislocation of this electrode occurred in 2 instances (3.3%) and an increase in threshold (exit-block) in 3 cases (5%) necessitated repositioning of the electrode.

[Evaluation of the interaction between blood and foreign material in the pump oxygenator during open-heart surgery in infants by scanning electron microscopy (author's transl)]. / Rasterelektronenmikroskopische Evaluation des Blut-Fremdkörperkontaktes in der Säuglings-Herz-Lungen-Maschine

Scanning electron microscopy was used to elucidate the interaction between blood and foreign material in the pump oxygenator during open-heart surgery in 7 infants. The loss of platelets upstream of the blood pump is caused by thrombogenicity. The pump itself causes massive destruction of platelets and red blood cells; thromboembolie up to 100 mu and foreign body particles up to 200 mu are being detached from the wall of the tubing to a large extent. The particulate matter is trapped in arterial line filter. Particles up to 40 mu and cellular aggregates up to 60 mu can pass through the filter and enter the patient's systemic circulation.

[Various blood-foreign body reactions in the heart-lung machine in heart valve replacement and aortocoronary bypass operations]. / Unterschiedliche Blutfremdkörperreaktion in der Herzlungenmaschine bei Herzklappenersatz- und aortocoronaren Bypass-Operationen.

Blood-foreign material interaction in the pump oxygenator was studied by means of scanning electron microscopy in 3 patients undergoing heart valve replacement (HVR) and 3 patients undergoing coronary bypass operation (CBO). While polyvinyl tubes show an average deposit of 60 thrombi/mm2 with 20--40 microns in size in CBO, bloodgas interface during HVR causes increasing thrombotic deposits (375 Mcthr/nm2, 25--50 microns in size). Distal to the pump the volume of particles may rise up 250 micrometer in HVR and up to 80 micrometer in CBO. In a 35 micrometer pore arterial-line-filter (Pall-Corporation) platelet clumps up to 1 mm in size are removed from circulating blood in HVR, and up to 300 micrometer thrombi in CBO. According to different platelet deposit proximal to the filter, more and larger thrombi can pass through the filter in HVR. Distal to the pump thromboemboli of 30--60 (maximum 90) micrometer in size can be observed in HVR. Particles of 20--35 (maximum 60) micrometer in size may pass through the filter and enter into the patient's circulation in CBO. As the results suggest, extracorporal circulation is more harmful for patients undergoing HVR than for those undergoing CBO.

[Animal experiments with a new intracardial pacemaker electrode]. / Tierexperimentelle Erfahrungen mit einer neuen intrakardialen Pacemkaer-Elektrode.

In order to reduce the rate of dislocation of intracardiac pacemaker electrodes, a new electrode was developed. The tip of this new electrode is helical and can be fixed between the trabecles of the right ventricle by clockwise rotation. Since the tip of this new electrode has no sharp hooks the myocard cannot be damaged by fixation.

[2 years of clinical experiences with lithium pacemakers]. / Zwei Jahre klinische Erfahrungen mit Lithium-Schrittmachern.

Between January 1974 and December 1976, 470 mercury-cell pacemakers and 353 lithium-cell pacemakers were implanted at Surgical Clinic A of the University Hospital of Zurich. Within the first 24 months 15.5% of the mercury-cell pacemakers had to be exchanged because of premature battery depletion and 1.3% due to dysfunction of electronic components. None of the lithium-cell pacemakers had to be removed for these reasons. In 6 lithium-cell pacemakers, however, overhaul was necessary because of sensing failure. One unit had to be removed after one year for local decubitus. In two cases, repositioning of the batteries was necessary because of local muscle stimulation.

[Stimulation rate of lithium powered pacemakers in the event of battery depletion]. / Frequenzverhalten von Lithium-Schrittmachern bei Batterieerschöpfung.

Between 1976 and 1977, 347 lithium powered pacemakers with capacity below 1.8 Ah have been implanted at Zürich University Hospital. 25 (7%) had to be explanted after an average of 37.3 months because of premature battery depletion, the reason for which was low resistance electrodes (Elema EMT 588 A and C) in CPI-502 UD and Telectronics 150B. Both types showed a drop in stimulation rate as an EOL-characteristic, as predicted by manufacturer. Rate controls at 6 month intervals have proven a reliable means of detecting premature failure. With ARCO Li-3D, prediction of battery depletion was possible only in one case out of 5 because of sudden and unpredictable EOL. In pacemaker dependent patients this type should be explanted by the end of the guarantee period at the latest.

Hemodynamic effects of atrial synchronization in acute and long-term ventricular pacing.

The acute and long-term hemodynamic benefit from atrial synchronization in ventricular (VAT) pacing has been investigated at rest and during exercise in 10 patients undergoing pacemaker implantation for complete A-V block. The results were compared to conventional (VOO) ventricular stimulation at rates of 70 BPM and 96 BPM. Cardiac index (CI) in VAT-pacing increased at rest by 8% and during exercise by 15% more than with VOO pacing (p less than 0.01). No significant change between the two different rates of asynchronous pacing was observed. CI at rest and during exercise was unchanged after 10 weeks of VAT-pacing. CI is regulated by change of stroke volume in VOO-pacing and by heart rate only with VAT-pacing. In contrast to earlier results with asynchronous ventricular pacing, the hemodynamic benefit of pacing in an atrial synchronized mode is long-lasting. Physiologic mechanisms regulate hemodynamics during exercise and in heart failure.

[Technic and long term results of pacemaker treatment with atrial electrodes]. / Technik und Langzeitresultate der Schrittmacherbehandlung mit Vorhofelektroden.

A new implantation technique in the upper lateral part of the right atrium has reduced the complication rate of atrial electrodes to less than 4% at 11 months' follow-up. P-wave amplitude and acute and chronic threshold are in the order of conventional ventricular electrodes. In 10 of 56 patients with atrial-triggered ventricular pacemakers the cardiac output at rest and during exercise was found to be respectively 8% and 17% higher than with fixed-rate ventricular pacing. This hemodynamic benefit is longlasting, in contrast to findings with non-atrial synchronized pacing.

[Surgical treatment of heart rhythm disorders]. / Die chirurgische Behandlung von Herzrhythmusstörungen.

Six patients underwent cardiac surgery for refractory tachyarrhythmias. Four had Wolff-Parkinson-White syndrome and 2 ventricular tachycardias after myocardial infarction. The results of preoperative electrophysiologic studies corresponded in 5 cases to intraoperative findings of epicardial and pace-mapping. These patients were free of symptoms for the 4-16 months' follow-up. In one patient with divergent results, tachycardia and preexcitation returned two months postoperatively. In the light of the foregoing the authors suggest surgical treatment for 1. preexcitation with life-threatening arrhythmias, 2. refractory ventricular tachycardias with coronary artery disease and 3. preexcitation in patients undergoing open heart surgery for other reasons.

[Cardiology 1995]. / Herzmedizin 1995.

Rapid progress in the field of cardiology calls for an almost continuous update on latest developments. In particular, this is the case with respect to indications for diagnostic and therapeutic interventions. The present contribution deals with some topics in this area. The first article elaborates on the theme of which diagnostic test is indicated, under what circumstances, and for which patient. Technical improvements in the surgical practice of coronary revascularization are discussed in the light of better therapeutic results. Unsolved questions of percutaneous dilatation (PTCA) are critically reviewed in a third article. Current problems in surgical treatment of valvular heart disease are dealt with in the fourth report. Finally, the enormous progress in pacemaker medicine that has accumulated since the world-wide first implant in 1959 by A. Senning is summarized in the last contribution.